This invention relates to friction braking systems and more particularly to aircraft friction discs with reinforced peripheral slots for use in multiple disc brakes.
In brake assemblies which employ a plurality of brake discs alternately splined to the wheel and axle of an aircraft, it is important to provide reinforced peripheral slots to the discs to relieve the severe stressing at these splined junctures. Formerly when the disc brakes employed discs of steel construction, the discs were able to withstand the shearing and compressive forces exerted thereon between the slots and the torque transmitting members. With the replacement of the steel discs with carbon composition discs it was important to provide reinforcing inserts at the peripheral slots since the carbon composites have less strength than steel. The inserts transmit the forces to the carbon discs, over a larger area reducing the contact stresses which increases the load capability of the carbon.
Some friction discs with reinforced inserts at the slots do not adequately transfer the load. In some structures the load is transmitted via radially disposed pins to the carbon discs. These discs require precise machining for the placement of the radial holes while simultaneously weakening the discs due to the removal of substantial material along the entire radial wall. In some structures the inserts for the peripheral reinforced slots transmit the forces to the insert rivets and then to the openings in the disc through which the rivets extend. These openings accept all of the discs loading and are therefore subject to undesirable very high stress concentrations. The brake disc problems relate equally well to clutches. The present invention utilizes an insert at the peripheral slots that engages the carbon disc and drives on the rotating member or transfers the stress to the stationary member without deleterious effects on the carbon composite materials. The insert has a pair of opposed faces which diverge to distribute the load providing an angle drive. A separate cap or clip is used to retain the inserts in position. Such structure eliminates peeling or fraying of the carbon composite heat sink material. The angle drive, when loaded, seats firmly against the carbon. The horizontal load due to misalignment between the wheel and brake are compensated for by the side component of the angle drive. The angle drive system allows the insert to float freely in the slot of the carbon disc thereby eliminating the loading of the attaching rivets.